SQL 中查询出学生成绩 平均分 方差 进行成绩一体化计算x = (成绩-平均分)/方差 结果x输出到textbox 但报错 求帮忙 应该是object 和int 等类型之间转换的问题代码如下
string trouble= "server=.;database=学生成绩智能管理系统;user id=sa;pwd=123123;";
SqlConnection cnn = new SqlConnection(trouble);
cnn.Open();
string trouble1 = "SELECT 课程表.成绩 FROM 成绩表 WHERE ........";
string trouble2 = "SELECT AVG(成绩表.成绩) FROM 成绩表,课程表,教师表 WHERE .......";
string trouble3 = "SELECT STDEV(成绩) FROM 成绩表 WHERE = .....";
SqlCommand t1 = cnn.CreateCommand();
t1.CommandText = trouble1;
t1.CommandType = CommandType.Text;
int a = Convert.ToInt32(t1.ExecuteScalar()); t1.CommandText = trouble2;
int b = Convert.ToInt32(t1.ExecuteScalar()); t1.CommandText = trouble3;
int c = Convert.ToInt32(t1.ExecuteScalar()); int d = (a - b) / c;
TextBox2.Text = d.ToString();
string trouble= "server=.;database=学生成绩智能管理系统;user id=sa;pwd=123123;";
SqlConnection cnn = new SqlConnection(trouble);
cnn.Open();
string trouble1 = "SELECT 课程表.成绩 FROM 成绩表 WHERE ........";
string trouble2 = "SELECT AVG(成绩表.成绩) FROM 成绩表,课程表,教师表 WHERE .......";
string trouble3 = "SELECT STDEV(成绩) FROM 成绩表 WHERE = .....";
SqlCommand t1 = cnn.CreateCommand();
t1.CommandText = trouble1;
t1.CommandType = CommandType.Text;
int a = Convert.ToInt32(t1.ExecuteScalar()); t1.CommandText = trouble2;
int b = Convert.ToInt32(t1.ExecuteScalar()); t1.CommandText = trouble3;
int c = Convert.ToInt32(t1.ExecuteScalar()); int d = (a - b) / c;
TextBox2.Text = d.ToString();
解决方案 »
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